entanglement i 13

8/9/2019 Entanglement I 13

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ENTANGLEMENT I

byRobert Nemiroff


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Physics X: About This Course

Officially "Extraordinary Concepts in Physics" Being taught for credit at Michigan Tech

o Light on math, heay on conceptso !nyone anyhere is elcome

#o text$oo% re&uiredo 'i%ipedia, e$ lin%s, and lectures onlyo (ind all the lectures ith )oogle at*

"+tarship !steris%" then "Physics "o http://bb.nightskylive.net/asterisk/viewforum.php?f=39


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ENTAN!E"ENT: $%E&%'E(

Two parti)les )an be )onsi*ere* entangle* when a +uantum state oftwo parti)les are linke*.

,an o))ur for parti)les that were-

)reate* at the same pla)e an* time.- )olli*e* at some pla)e an* time.Typi)ally involves- spin- momentum


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ENTAN!E"ENT: $'T&$N'0"

ositronium- ele)tron an* a positron orbiting- *e)ays +ui)kly into two *aughter photons

1aughter photons of ositronium haveo entangle* spins 2oppositeo entangle* momenta 2opposite


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ENTAN!E"ENT: E& A&A1$4

- 5936 paper by Einstein7 o*olsky7 an* &osen 2E&- Thought by E& to show that

o 8" is in)ompleteo hi**en variables must eisto otherwise 8" spooky a)tion at a *istan)e

- origin of entangle* parti)les i*ea

- ;asis for ;ell


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- imple version of E& eperiment:- A sour)e *e)ays into two parti)les 2entangle*

o one goes to Ali)e 2A7 the other to ;ob 2;o the total angular momentum is >ero


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'f Ali)e measures the spin of her parti)le to be spin up on the >ais7will Ali)e know that ;ob will measure his entangle* parti)le to be spin*own on the >ais before;ob knows it?

5. @es7 Ali)e is that smart.. No7 that woul* re+uire BT! )ommuni)ation.3. @es7 but only in a statisti)al sense.C. 1epen*s on how mu)h Ali)e is paying her psy)hi).


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5. @es7 Ali)e is that smart.

'n fa)t7-

'f Ali)e an* ;ob both measure > ais spino will A!(A@ get opposite > spin- 'f Ali)e an* ;ob both measure ais spin

o will A!(A@ get opposite spin


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1oes this7 by itself7 mean that Ali)e an* ;ob )an )ommuni)ate BT!?

5. @es.. No.

3. "aybe so.


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. No.

't )oul* be that the parti)les were )reate* ea)h having opposite spins.This )oul* have been *one with tennis balls this )orrelation re+uires

only )onservation of momentum7 not BT! )ommuni)ation. Thatparti)les are )reate* with attributes that are then fro>en is part of thei**en %ariables 2% interpretation of +uantum me)hani)s.


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Net7 Ali)e measures her parti)le as spin up on >ais an* ;obmeasures his parti)le>y.


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3. alf the time spin up7 half the time spin *own.;ob measurement is in*epen*ent of Ali)e


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ENTAN!E"ENT: !$,A!'T@

The prin)iple of lo)ality states that obe)ts )an only be affe)te* by theirimme*iate surroun*ings.

Entanglement appears to violate lo)ality but not in su)h a way that

allows *istant observers to sen* information to ea)h other faster thanthe spee* of light.

entanglement i 13

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